Piston ring for automatic weapon with breech-unlocking piston



3,333,510 PON N M LEMANN G AUTOMATIC WEA TH BREECH-UNLOCKIN ISTO Filed Oct. 22, l 5

7 1967 E fiON RIN United States Patent Ollice 3,333,510 Patented Aug. 1, 1967 3,333,510 PISTON RING FOR AUTOMATIC WEAPON WITH BREECH-UNLOCKING PISTON Ernst Miihlemann, Zurich, Switzerland, assignor to Oerlikon-Buhrle Holding A.G., Zurich, Switzerland Filed Oct. 22, 1965, Ser. No. 501,399 Claims priority, application Switzerland, Nov. 11, 1964, 14,548/ 64 3 Claims. (Cl. 89-193) ABSTRACT OF THE DISCLOSURE A gas operated automatic firearm wherein the piston for operating the breech mechanism is provided with a conical surface at its front and also an insert on the piston having a flange. A slotted resilient ring with a conical surface cooperates with the conical surface on the piston and the ring is located between the flange of the insert and the piston conical surface so that when subjected to the pressure of the explosion gases the ring will expand and be pressed against the wall of the gas cylinder.

This invention relates to an automatic firearm in which the gas-filled space on one side of the piston is sealed off by at least one slit ring fitted to the piston.

The piston rings used for such weapons in the prior art suffer from the drawback that the heavy stresses imposed upon them by automatic weapons With a high rate of fire cause them either to break or to lose their spring tension and hence obturating powers after a short operating period, leading to rapid fouling of the gas-piston cylinder with powder-smoke deposits which have an adverse elfect on the proper functioning of the gas piston. An object of the present invention is to eliminate this drawback.

A further object of the invention is to provide a male cone on the piston with its apex pointing in the direction of the piston chamber over which fits a female conical surface on the piston ring, which latter is forced apart by the pressure of the explosion gases.

A still further object is to provide an arrangement wherein the ring does not need to be under stress the whole time and the pressure of the ring against the cylinder walls which is required for obturation being created anew with each shot fired, i.e. each time that explosion gases enter the cylinder the ring is forced over the male cone on the piston and hence expands radially against the cylinder walls.

A further object is to provide an arrangement wherein the ring can be so massively dimensioned as to eliminate breakages.

With the above and other objects in view which will become apparent from the detailed description below, a preferred embodiment of the invention is shown in the drawings in which:

FIGURE 1 is a longitudinal cross-sectional view of a portion of the firearm.

FIGURE 2 is a partial cross-sectional view taken along section line II-II of FIGURE 1, and

FIGURE 3 is a partial cross-sectional view taken through the piston ring.

FIGURE 1 shows the barrel 5 fitted to the receiver 4 by means of a bayonet joint 6. The receiver 4 is provided with a housing portion 7, into which the insert 8 is screwed. Together with the housing portion 7, the insert 8 forms a cylinder 9 in which the piston 10 can slide.

This latter transmits its motion via the rod 11 to the breech mechanism in order to unlock the latter after a shothas been fired in a manner which is well known, and will not therefore be described here in further detail.

At the rear end of the cylinder 9 a packet 12 of circular springs is located, which serves to buffer the piston 10 at the rear end of its stroke. The rear portion of the piston-rod 11 is in the form of a hollow tube accommodating the return spring 13. The rear end of the spring 13 abuts against a part of the receiver 4 which is not shown in the drawing.

The front end of the insert 8, at the left in FIGURE 1, extends in front of the housing portion 7 of the receiver 4 in the form of a nose 14, perforated by a bore 15 which leads explosion gases from the gas-bleed passages 17 and 19 to the chamber of the cylinder 9.

The piston-head insert 24 is screwed into the tapped hole 23 of the piston 10. The front end of the insert 24 is in the form of a flange 25. The conical surface 28, which opens out towards the rear, terminates at the guide surface 27 of the piston 10. The ring 29, broken by the slot 30, has the same external diameter as the piston guide-surface 27, and slides in the cylinder 9. Its internal cylindrical surface 31, see FIG. 3, Widens out in the form of a female cone 32, whose angle corresponds to that of the male cone 28 of the piston 10. The internal diameter of the ring 29 is smaller than the external diameter of the flange 25 of the piston-crown insert 24. The axial play of the ring 29 is limited in front by the rear surface of the flange 25 and behind by the conical surface 28 of the piston 10.

The above mentioned construction causes the pistonring to function in the following manner:

When a bullet has passed the gas-bleed port in the gun barrel, explosion gases pass through the gas-bleed passage and the bore 15 of the insert 8 to the cylinderhead space 9.

The gas-piston 10 is forced backwardly by the pressure of the gases and unlocks the breech mechanism of the gun. The ring 29 is also subjected to the gas pressure, which presses it backwardly over the conical surface 28 of the piston 10, so that it expands elastically until its outer surface 33 is forced against the Walls of the cylinder 9 to form a gas-seal. When the bullet has left the muzzle of the gun the pressure inside the barrel 5 falls back to atmospheric pressure, as does also that in the cylinder-head space 9, upon which the ring 29 contracts again and hence does not hinder the return of the piston 10 to its starting position under the action of the return spring 13.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the form hereinbefore described and illustrated in the drawings being merely a preferred embodiment thereof.

I claim:

1. An automatic firearm comprising a barrel having a gas-bleed port, a receiver mounted on said barrel, a gas cylinder in said receiver having a gas chamber, means connecting said chamber of said cylinder with said gasbleed port, a piston reciprocating in said cylinder to operate the breech mechanism of said firearm, an insert for said piston having a flange, a conical surface on said piston having its apex pointing in the direction of said cylinder chamber and a slotted resilient ring having a conical surface cooperating with said first named conical surface, said ring being located between said flange and said conical surface on the end of said piston, so that when subjected to the pressure of the explosion gases said ring will expand and the outer perimeter thereof will be pressed against the Wall of said cylinder.

2. An automatic firearm as set forth in claim 1 wherein said flange on said insert has substantially the diameter of said cylinder chamber and said ring is mounted on said conical surface of said piston with axial play.

3. An automatic firearm as set forth in claim 2 wherein said ring when unexpanded has an internal diameter less than the external diameter of said flange.

4 References Cited UNITED STATES PATENTS 1,333,023 3/1920 Johnston 277-170 3,114,290 12/1963 Harvey et a1 8926 FOREIGN PATENTS 233,976 10/ 1962 Austria.

2,500 10/ 1853 Great Britain. 638,164 5/1950 Great Britain.

BENJAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY, Assistant Examiner. 

1. AN AUTOMATIC FIREARM COMPRISING A BARREL HAVING A GAS-BLEED PORT, A RECEIVER MOUNTED ON SAID BARREL, A GAS CYLINDER IN SAID RECEIVER HAVING A GAS CHAMBER, MEANS CONNECTING SAID CHAMBER OF SAID CYLINDER WITH SAID GASBLEED PORT, A PISTON RECIPROCATING IN SAID CYLINDER TO OPERATE THE BREECH MECHANISM OF SAID FIREARM, AN INSERT FOR SAID PISTON HAVING A FLANGE, A CONICAL SURFACE ON SAID PISTON HAVING ITS APEX POINTING IN THE DIRECTION OF SAID CYLINDER CHAMBER AND A SLOTTED RESILIENT RING HAVING A 